My only worry about Quicksilver's inclusion in this film are; Marvel might not promote DOFP, I mean they have a say for tie-in merchandises and they would make Quicksilver super important in Avengers 2 just to top DOFP's Quicksilver.

If you take a look at the Marvel 10Ks prior to the Disney purchase, Marvel controls tie-in merchandise for their liscensed properties. DOFP will have the same tie in merchandise as XM:FC and The Wolverine - none.